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Shuttle Mission to End Today Because of Faulty Generator

By William Harwood
Special to The Washington Post

The potential for an explosion in an electrical generator forced the Columbia astronauts Sunday to cut short a planned 16-day science mission and to prepare instead for a quick flight home today.

The decision to abort the 83rd shuttle flight was a crushing disappointment to scores of scientists and engineers who began planning the complex series of microgravity experiments more than three years ago. Only a handful of the 33 planned experiments can be undertaken on a mission that cost about $500 million.

"These experiments are important to us and we want to see them run," said mission scientist Michael Robinson. "Hopefully, they will run in the future (on another flight) and we're hanging on to that glimmer of hope."

Columbia's seven astronauts Sunday shut down the balky generator and started preparing the orbiter for a landing Tuesday at the Kennedy Space Center.

While two other electricity-generating fuel cells are working properly, NASA flight rules require a shuttle crew to head for home when one fails, to protect against the possibility of subsequent malfunctions.

"This is not an emergency situation," said shuttle program director Tommy Holloway. "It's a prudent thing to do.

NASA managers say they hope the problem with Columbia's electrical generator will not affect plans to launch the shuttle Atlantis next month on a critical flight to dock with the problem-plagued Russian Mir space station.

The flight of shuttle Columbia was derailed Sunday by a subtle, not-yet-understood problem in fuel cell No. 2, one of three electrical generators on the shuttle that combine hydrogen and oxygen to produce both electricity and the crew's drinking water.

Each $5 million power plant is made up of 96 cells arranged in three so-called substacks of 32 each. Engineers monitor the performance of a given fuel cell by comparing the output of half the cells in each substack against the other half.

Shortly after Columbia's launch Friday, engineers noticed a slight discrepancy in the voltage from one of the substacks in fuel cell No. 2. As the flight progressed the mismatch increased, indicating low voltage in a single cell.

Low voltage generates heat, and engineers were concerned that if the fuel cell continued to operate, enough heat could be generated to burn through membranes separating hydrogen and oxygen.